1. Field of the Invention
The present invention relates to a method and a device for driving a compaction machine.
2. Description of the Prior Art
Customarily, in compacting the ground, or materials spread over the latter, a machine is used which includes, for example, rollers which may or may not be vibratory, of steel or with tires.
The driver of the machine carries out by means of the latter, a sufficient number of round trips so that the soil of this area reaches the desired densification.
Ideal compaction, if the surface to be compacted is homogeneous at the start, is such that the machine is passed an equal number of times over each point of this area.
Such an ideal is difficult to achieve by the present technique, which calls mainly on the skill and the regularity of the driver of the machine. To obtain a regular progress of the work, the latter must offset the area covered by the machine on each pass to and fro, that is to say if one calls "work length L" the distance traversed in reverse travel by the machine in a round-trip constituting a pair of passes, and "advance length la" the additional distance traversed in forward travel in the pass which follows this round-trip, then L and la must be kept constant simultaneously, or, stated more simply, the machine must advance each time by a constant length (L=la), and withdraw by a length L, also constant, which is impossible to achieve strictly in the absence of accurate fixed points. In addition, the width of the area to be compacted is often greater than the width processed by the machine in a passage, or "track", which considerably complicates the problem, since after having compacted one track over a certain length, the driver must abandon it to process a length of the adjacent track, and then, after having treated the whole width of the area to be compacted, he must come back to the first track ad resume it at the point where he had left it. Considering that the total width of the area to be compacted is not perforce an exact multiple of the width of the track, one is obliged to accept a certain overlap between one track and its neighbor, which generally is without serious consequences, since the irregularity which can result therefrom is in the longitudinal direction, and less troublesome than if it were transversal.
On the other hand it is important for all the tracks to be compacted in the same manner, and to have undergone the same number of passages.
In the case where materials previously spread by a laying or spreading machine must be compacted, the width of this machine is such that it covers simultaneously two or three tracks with the material to be compacted. It has been observed that it is not possible to obtain a good profile if one track is compacted completely before passing to the neighboring track. Hence it is necessary to operate, for example in the following manner: a round-trip is made over one track and then one passes to another track; when all the tracks have received a round-trip, the cycle is recommenced in the proportion of one round-trip each time on each time, with an offset by an advance length la.
It is an object of the present invention to enable the driving of the machine to be effected such that the work of compaction is in accordance with a pre-established program whilst leaving to the driver the possibility of intervening according to the hazards of the work site, if the latter should require it.
It has already been proposed in the old French Patent No. 459,802 to automatize the changing of the operation of a compactor: a simple mechanical device including a screw rotated by the drive wheel causing a bolt to advance or withdraw according to the direction of working and a bolt acted alternately on two stops one controlling the forward operation, the other the rearward operation. This device hence only permitted round-trips without advancing, and was intended for certain special operations comprising short parameters.